CBET Anatomy and Physiology Basics 5 — Questions and Answers
Question 1: During inspiration, the diaphragm contracts and moves inferiorly, causing intrathoracic pressure to:
- Increase, pushing air out of the lungs
- Decrease, drawing air into the lungs (Correct answer)
- Remain unchanged due to chest wall recoil
- Equalize with atmospheric pressure immediately
Correct answer: Decrease, drawing air into the lungs
Diaphragm contraction increases thoracic volume, which decreases intrathoracic (pleural) pressure below atmospheric, causing air to flow in.
Question 2: Which ion is primarily responsible for the depolarization phase of a cardiac action potential?
- Potassium (K⁺) influx
- Sodium (Na⁺) influx (Correct answer)
- Calcium (Ca²⁺) influx
- Chloride (Cl⁻) influx
Correct answer: Sodium (Na⁺) influx
Rapid Na⁺ influx through fast voltage-gated sodium channels causes the sharp depolarization (phase 0) of the cardiac action potential.
Question 3: A ventilator-dependent patient has a tidal volume of 500 mL and a respiratory rate of 12 breaths/min. What is the minute ventilation?
- 500 mL/min
- 4,200 mL/min
- 6,000 mL/min (Correct answer)
- 7,200 mL/min
Correct answer: 6,000 mL/min
Minute ventilation = tidal volume × respiratory rate = 500 mL × 12 breaths/min = 6,000 mL/min (6 L/min).
Question 4: The sinoatrial (SA) node is located in which chamber of the heart?
- Left atrium
- Right atrium (Correct answer)
- Right ventricle
- Interventricular septum
Correct answer: Right atrium
The SA node is embedded in the wall of the right atrium near the junction with the superior vena cava and serves as the heart's primary pacemaker.
Question 5: Which blood vessel carries oxygenated blood from the lungs back to the heart?
- Pulmonary artery
- Pulmonary vein (Correct answer)
- Aorta
- Superior vena cava
Correct answer: Pulmonary vein
The pulmonary veins (four total) carry oxygen-rich blood from the lungs to the left atrium, making them unique among veins.
Question 6: The myelin sheath surrounding nerve axons is produced by which cells in the peripheral nervous system?
- Astrocytes
- Oligodendrocytes
- Schwann cells (Correct answer)
- Microglia
Correct answer: Schwann cells
Schwann cells myelinate peripheral nerve axons, with each Schwann cell wrapping around a single axon segment, unlike oligodendrocytes which serve the CNS.
Question 7: In a patient connected to an ECG monitor, the PR interval represents the time for electrical conduction from the:
- SA node through the atria to the ventricular myocardium
- Bundle of His through the Purkinje fibers
- AV node through the bundle branches to Purkinje fibers
- SA node to the AV node, through the His-Purkinje system to the ventricles (Correct answer)
Correct answer: SA node to the AV node, through the His-Purkinje system to the ventricles
The PR interval (normally 0.12–0.20 seconds) measures the total time from SA node firing through atrial depolarization and AV nodal delay to the onset of ventricular depolarization.
CBET Anatomy and Physiology Basics 5
During inspiration, the diaphragm contracts and moves inferiorly, causing intrathoracic pressure to: